ABSTRACT
By means of differential scanning calorimetry, effects of systematic series of Group I and VII ions on the phase state of model multibilayer dimyristoylphosphatidylcholine (di(14:0)PC) membranes have been studied at a lipid/ion molar ratio of 3/1. The sign-changing correlations between the ionic radii of cations and temperature shifts of di(14:0)PC phase transition were obtained. For cosmotropic Li+ and Na+, the observed shifts were positive (LiCl: deltaT(m) = 0.6 degrees C; deltaT(p) = 1.9 degrees C), whereas chaotropic K+ and Rb+ presence resulted in negative shifts (RbCl: deltaT(m) = -0.3 degrees C; deltaT(p) = -2.5 degrees C). The anions (Cl-, Br-, I-) showed a similar effect increasing with the ions chaotropicity. An essentially weaker effect of Cs+ as compared to other alkali metal ions (CsCl: deltaT(m) approximately 0 degrees C; deltaT(p) = -0,1 degrees C) can be one of the reasons of its accumulation in living organisms. Generalization of all available data allowed us to specify some important factors of lipid-ion interactions that should be taken into account in further investigations in this field.